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-   -   Converging-Diverging part (http://www.cfd-online.com/Forums/fluent/27992-converging-diverging-part.html)

Jungyoon hahm October 31, 2000 20:18

Converging-Diverging part
 
Hi all, I try to analsys fluid film between flat plate and concave plate(so it has converging and diverging part) But the result says diverging part have negative pressure. It's somewhat stange to me I want to change this to seperation or other pressure value. How can I do?

Thanks, all


Phil November 1, 2000 11:01

Re: Converging-Diverging part
 
I don't know if I understand your question but negative pressures are relativ to the operation pressure.

If this is not your problem please explain more detailed you geometry, the system (incompressible fluid properties, lam or turb. case etc.).

Regards Phil

Jungyoon hahm November 1, 2000 13:31

Re: Converging-Diverging part
 
Thanks for your message. My system is fluid film formation between plate. It's incompressible and laminar flow. There is inlet and outlet.(have different pressure) The lower plate is flat as many simple problem. But the upper plate has geometry like parablic and it's center is located above the upper plate(so that is concave and has converging diverging part consecutively). There is pressure to support this fluid film. Due to this goemetry have converging and diverging part consecutively, there is negative pressure at the diverging part. So I want to find analysis method. One of this may be considering the seperation of the fluid film. Then how can I change the pressure value into the fluent?(I want to constrain the pressure will be same as separation condition)


Max November 17, 2000 12:04

Re: Converging-Diverging part
 
Phil, is that all turbulent flow is unsteady state?

Max

Phil December 15, 2000 09:19

Re: Converging-Diverging part
 
I do not understand what you are asking for?? So if you mean that turbulent flow is unsteady you are basicly right. This is caused by fluctuating values for each mean flow property. However you can simulate it assuming a steady state. Even if this is not right you get a result which is, if converged, a result of an unsteady flow.

Regards Phil


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